This invention relates to electrical connectors. More particularly it relates to connectors adapted to receive a flat integrated circuit device package.
The high density packaging of electronic equipment, particularly data processing systems, may involve the installation of pluggable integrated circuit packages in receptacles or connectors. The connectors in turn are mounted on an interconnection medium, such as a printed circuit board. The electrical contact pins within the connector provide electrical circuit paths between the integrated circuit package contact pads and the conductor termination lands or conductor pads on the printed circuit board. Hold down means are often provided to apply a clamping force to the installed integrated circuit package to insure that a uniform electrical connection is made between the integrated circuit package and the connector. One such packaging system is described and claimed in the referenced U.S. pat. application Ser. No. 513,283, filed Oct. 9, 1974 by Robert E. Braun et al now U.S. Pat. No. 3,946,276, entitled "Packaging System For Electronic Equipment", which is also assigned to the same assignee as the present invention. The present invention involves an improved alternative to the connector as disclosed in the above patent application.
The leadless integrated circuit packages which are generally used in this or similar packaging systems often have a contact pad spacing of 0.05 inch or less between adjacent contact pads. The contact pins of the prior art connectors are all in the same vertical plane. Consequently, the circuit board on which the package is mounted had to also provide a correspondingly small conductor pad spacing in order to interface with the contact pins projecting from the lower surface of the connector. While such a circuit board arrangement has been made with satisfactory results, the yield in high volume production is expected to be somewhat low due to the extremely small spacing between adjacent contact pin receiving elements, or conductor pads, on the printed circuit board. One suggested method of obviating this predicament is to stagger the connector contact pins in a zig-zag pattern along each side of the connector. For example, see U.S. Pat. No. 3,846,737 Spaulding entitled "Electrical Connector Unit for Leadless Circuit Device" or U.S. Pat. No. 3,831,131 Woodcock et al entitled "Integrated Circuit Package Connectors". However, such a connector "pin-out" configuration does not lend itself to optimum circuit board manufacturing techniques. Computerized automatic routing equipment is often used by circuit board manufacturers to automatically print the design on the masks used to etch the conductors on the circuit board in the desired pattern. In order to accommodate the zig-zag connector pin-out configuration, many man hours must be consumed in order to program the automated routing equipment. But even more importantly is that valuable computer time is used to control the routing equipment. The staggered pin-out requires additional computer time to route the conductors around the non-uniformly spaced conductor pads. Moreover, the staggered conductor pad spacing limits the number of conductors that can be run through the conductor pad area on the board.
In the packaging system of Ser. No. 513,283, the connector must be mounted level with respect to the supporting printed circuit board. This planarity is required in order to insure that the package contact pads provide equal downward force on the connector contact pins after the package has been clamped against the cooling frame. An even distribution of pressure between the package contact pads and connector contact pins is essential for proper electrical connection. It is general practice to provide stand-off bumps to lift the bottom of the connector off of the surface of the printed circuit board. This is to facilitate cleaning of the printed circuit board after soldering (e.g. flux removal). However, the randomly placed stand-off bumps used on commercially available connectors do not provide satisfactory results when accurate planarity with the printed circuit board is required. For example, one of the stand-off bumps may directly abut the top surface of the printed circuit board, whereas another stand-off bump may abut a conductor on the printed circuit board. Accordingly, the connector may have a tendency to wobble and does not provide a suitable level reference for proper connection with the leadless package in the packaging system disclosed in U.S. Pat. No. 3,946,276.